sandy wrote:
For a certain distribution, the measurement 12.1 is 1.5 standard deviations below the mean, and the measurement 17.5 is 3.0 standard deviations above the mean. What is the mean of the distribution?
A. 13.8
B. 13.9
C. 14.0
D. 14.1
E. 14.2
Another approach:
Let M = the mean
Let D = standard deviation
12.1 is 1.5 standard deviations below the meanSo,
M - 1.5D = 12.1 17.5 is 3.0 standard deviations above the meanSo,
M + 3D = 17.5We have the system:
M - 1.5D = 12.1M + 3D = 17.5Multiple both sides of the top equation by 2 to get:
2M - 3D = 24.2M + 3D = 17.5ADD the two equations to get: 3M = 41.7
Solve to get: M = 13.9
Answer: B
Cheers,
Brent
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Brent Hanneson - founder of Greenlight Test PrepSign up for our GRE Question of the Day emails